Process of treating water



Reiuued June 7, 1938 Ludwig Rosenstein, San Francisco,

signor, by mesne assi Calif., asgnmentn-to Hagan Gorporation.Pittsburgh, Pa. a corporation of Pennsylvania No Drawing. Original No.2,038,316, dated April 21, 1936, Serial No.

Reissue No. 20,360, Serial No. 120,241, January 12, 1937.

plication for reissue rial No. 164,493

13 Claims.

This invention relates to a process for avoiding the deposition ofcalcium carbonate from natural waters at their natural temperatures.

This invention is particularly useful where fertilizing material isdelivered to soils by means of natural waters.

According to a recently devised process ammonia is passed intoirrigation water in such controlled low amounts that a concentration ofammonia is produced in the water which is so low that injury of thevegetation will not result upon the water coming into contact with thevegetation.

It has been found that where water containing amounts of calcium andbicarbonate is used as a carrier for the ammonia above mentioned calciumcarbonate precipitates because of the reaction:-

Cs ++HCOI+NH,=CaCO;+NH

solid The precipitates so formed from natural waters also containmagnesium carbonate. To avoid repetition the term calcium" will be usedthroughout this specification whenever both calcium and magnesiumcompounds are intended.

The precipitation of calcium carbonate is the factor which limits theamount of ammonia which can be added to the water. For example, with aparticular irrigation water (applied to an orange grove) having acalcium concentration of one hundred and twenty parts per million ofwater and nearly the equivalent amount of bicarbonate, it was found thatthe ammonia passed into the water had to be limited to twelveandone-half pounds per hour when water was applied at the rate of 225,000lbs/hr. Any larger introduction of ammonia resulted in the fatalplugging of the pipe lines, valves and the like, due to the heavyprecipitation of calcium carbonate.

Application of ammonia at the above low rate was totally inadequate tosupply the needs of the orange trees. In order to overcome thisdifliculty in this and similar cases, it was necessary to devise somemeans of either preventing the precipitation of calcium carbonate orinhibiting its formation for a suillcient time period so that all waterwould leave the system before precipitation took place. or causing theprecipitated particles to be of such physical character that they wouldbe swept out of the system by the flow of water and would not deposit onthe surfaces of the pipes and valves forming the distribution system.

It is an object of this invention to devise a method of preventing thedeposition of calcium carbonate from waters. It is a further object of38,535, August 30. dated May 11, 1937,

This ap- September 18, 1937, Se-

this invention to devise a process which will enable ammonia to be addedto irrigation water in greater quantities than heretofore.

It is another object of this invention to devise means which will avoiddeposition of calcium carbonate produced by the addition of ammonia towater.

In brief, my invention comprises the addition of substances to waterwhich will avoid or delay the precipitation of calcium carbonate or willproduce such precipitate in so finely divided a stake that it will notadhere to the pipes and valves through which the water is passed.

, The following is an example of the use of a precipitation retardingcolloid. A hay infusion was made by steeping grams of alfalfa hay in oneliter of water and allowing the hay to remain until bacterial action hadprogressed to a considerable degree. The liquid containing the infusionwas drained oil and added in the amount of one cubic inch of liquid toone hundred cubic inches of irrigation water containing calciumbicarbonate in large amounts. After the addition of ammonia to the waterit was found that the precipitation of calcium carbonate was delayed forapproximately twenty minutes. The precipitate ultimately formed was veryfine and nonadherent. v

I have found that certain chemicals when added to the water will alsoretard the precipitation and render the precipitate finely divided andnonadherent.

The following is an example of these latter compositions. To a watercontaining 142 parts per million of calcium ion, ammonium hexa metaphosphate was added so as to produce a meta phosphate concentration offrom 0.50 part per million to 1 part per million. Thereafter suificientammonia was added into the water to produce an ammonia concentration of500 parts per million. This would normally cause the rapid precipitationof large amounts of calcium carbonate. No precipitation took place forseveral hours. Instead of ammonium meta phosphates I may use other metaphosphates such as sodium meta phosphates, potassium meta phosphates orI may use meta phosphoric acid. H

A significant part of this discovery is the very small amount of thereagent required. his well 1 taining the largest amount .of calcium isknown to be 0-10 and in the known use of this reagent amounts are usedwhich are equal to or exceed the stoichiometric amount. For example,again considering a water containing 142 parts per million of calciumion, the addition of 1086 parts per million of sodium hexa metaphosphate would be required in order to combine all the calcium into thecomplex ion K OF I have found that it is not necessary to combine allthe calcium into the complex ion and that precipitation of the calciummay be i hibited by using quantities of reagent far below thestoichiometric amount.

According to my discovery 1/ 2000 to 1/1000 of this stoichiometricamount is sufiicient to accomplish the desired result when sodium hexametaphosphate, potassium hexa metaphosphate or ammonium hexametaphosphate are used. Therefore when I speak of the addition of themetaphosphate to the water in substantially less than stoichiometricamounts, I mean the addition of a small fraction of the stoichiometricamount.

It should be understood that in this specification and in the claimsattached hereto, the term alkali-metal includes ammonium.

I have also found that other soluble phosphates have the property ofaffecting the precipitation of calcium carbonate. For example, sodiumpyrophosphate, orthophosphoric acid and in general salts oforthophosphoric acid all display the effect of delaying theprecipitation of insoluble calcium compounds or of affecting theirphysical character so that the precipitate is finely divided andnon-adherent.

The phosphates such as meta phosphates and pyrophosphates in which theratio of phosphorus pentoxide to metallic or hydrogen oxide is greaterfusion and the like also affect the rate of precipitation and physicalcharacter of the precipitate favorably for the objective desired.

The treating reagent can be added to the water by any suitable meteringdevice.

Where ammonia is added to the irrigation'water from cylinders ofanhydrous ammonia, amounts of treating reagent can be added to the waterat the same time and in proportion to the ammonia flow by well knowndevices. It'is preferable in the case of meta phosphate or metaphosphoric acid that it be introduced into the water at a point upstreamfrom the point of ammonia injection.

I claim as my invention:

1. Process of retarding the precipitation of calcium carbonate fromnatural waters comprising adding to the water an alkali-metal hexa metaphosphate in amounts not exceeding one thousandth part of thestoichiometric amount required to react with said calcium to formcalcium metaphosphate whereby precipitation of calcium carbonateresulting from the addition of alkali is prevented.

2. In a process of supplying increased amounts of fertilizer to soils bymeans of irrigation water, the step of adding a calcium carbonateprecipitation retardant to said water in amounts only suiiicient toprevent the precipitation of calcium carbonate upon the subsequentaddition of ammonia to said water.

3. In a process of supplying increased amounts of fertilizer to soils bymeans of irrigation water, the step of adding meta phosphate to saidwater in amounts only sufflcient to prevent the precipitation of calciumcarbonate upon the subsequent addition of ammonia to said water.

4. In a process of supplying increased amounts of fertilizer to soils bymeans of irrigation water, the-steps of adding sodium meta phosphate toa flowing stream of water containing calcium compound in less than thestoichiometric amount required to react with said calcium compound,thereafter passing ammonia into said water and supplying said treatedwater to the soil.

5. Procem for inhibiting in natural waters the precipitation of calciumcarbonate resulting from the addition of alkali consisting in adding tothe water an alkali-metal hexa meta phosphate in substantially less thanstoichiometric amounts.

6. Process for inhibiting in natural waters the precipitation of calciumcarbonate resulting from an increase in carbonate ion concentrationconsisting in adding to the water an alkali-metal hexa meta phosphate insubstantially less than stoichiometric amounts.

7. Process for supplying increased amounts of fertilizer to soils bymeans of irrigation water comprising adding a calcium carbonateprecipitation retardant to water in an amount suificient to prevent theprecipitation of calcium carbonate from said water upon the subsequentaddition of ammonia, adding ammonia to said water, thereafter supplyingsaid treated water to the soil.

8. Processfor supplying increased amounts of fertilizer to soils bymeans of irrigation water comprising adding a soluble phosphate to saidwater in amounts suihcient to prevent the precipitation of calciumcarbonate from said water upon the subsequent addition of ammonia,adding ammonia to said water, thereafter supplying said treated water tothe soil.

9. Process for supplying increased amounts of fertilizer to soils bymeans of irrigation water comprising adding a soluble meta phosphate towater in amounts sulflcient to prevent the precipitation of calciumcarbonate upon the subsequent addition of ammonia, adding ammonia tosaid water, thereafter supplying said treated water to the soil.

fertilizer to soils by means of irrigation water phosphate insubstantially less than stoichiometric amounts.

12. A process for inhibiting in calcium-containing waters theprecipitation of calcium carbonate resulting from an increase incarbonate ion concentration consisting in adding to the water a verysmall amount of a. water-soluble molecularly dehydrated phosphate.

13. A process for inhibiting in calcium-containing waters theprecipitation of calcium carbonate resulting from an increase incarbonate ion concentration, consisting in adding to the water awater-soluble molecularly dehydrated phosphate in an amount of the orderof a very few parts per million.

LUDWIG ROSENSTEIN.

